1. Field of the Invention
This invention relates to dump trucks having means to heat the dump body.
More specifically, this invention relates to engine exhaust diverter valves which direct engine exhaust gases to a header surrounding the dump body of the dump truck or, depending upon the position of the dump body in respect to the valve, directs the engine exhaust gases to an exhaust pipe.
2. Description of the Prior Art
In the design of heavy duty off highway dump trucks it has been found to be advantageous to heat the dump body in order to prevent the load from freezing to the dump body which, of course, hampers the unloading of the dump body. Heating the dump body also effectively aids in the release of cohesive material such as wet clay, muck and coral rock.
Heating of the dump body has been accomplished through the use of the engine exhaust gases passing through a manifold formed integrally with the dump body. However, a problem is encountered in effecting this method of dump body heating as the dump body will be lifted away during a dumping cycle from the exhaust system of the engine in most cases. With this break in the exhaust system the exhaust gases and particulates are discharged in proximity to the air intake filters and the vehicle cab. This exhaust emission has a tendency to be drawn into the air cleaners and causes premature blocking of them. Additionally, the presence of these exhaust emissions make the cab somewhat uncomfortable.
Thus valving systems have been developed which direct the exhaust gas away from the engine in the cab. Typically these systems are so-called flapper valves which have a linkage associated therewith to position the valve to direct the flow of exhaust gases. The linkage system requires occasional adjustment and maintenance in order to operate properly.
The assignee of this invention has used a valve having a plate biased between a circular exhaust orifice and a concentric cylindrical port concentric with the exhaust orifice such that the plate was biased by internal springs between a position blocking the concentric cylindrical port when the dump body was down and a position blocking the circular exhaust orifice when the dump body was in a dumping attitude. The springs resided in the path of the flow of the hot gases and were thus subject to yielding after long term exposure to said heat.
The invention disclosed herein overcomes difficulties with prior art structures by providing a self-adjusting valve having no bothersome linkages and no parts which would be effected by heat of the exhaust gases.